Moodle : is it possible to access user from javascript ONLY

My purpose is simply being able to retrieve basic user info (id, username, lastname, firstname) in javascript on ANY moodle page WITHOUT having to create a plugin. I've seen that there is a javascript global variable in Moodle : `M` but no user info in there. Is there a way to access user info (id at least) from a logged in user on any page only in javascript another way ? I've tried the [generico filter][1] to create a block i would be able to retrieve information from <span data-firstname="@@USER:firstname@@" data-lastname="@@USER:lastname@@" data-userid="@@USER:id@@" id="useriddata"></span> But since i want it on any page, i've tried on the Moodle > Extra HTML textarea. Sadly it doesn't work since the HTML seems not to be filtered there. Creating a plugin for such a small information seems wrong. What can i do ? [1]: https://moodle.org/plugins/filter_generico